The present invention relates to an inkjet printing device, printing system and a method of executing a printing operation on a fabric.
Conventionally, image data is created on a personal computer (hereinafter, occasionally referred to as a PC) with displaying an image represented by the image data being displayed on a monitor device. Such image data is converted into print data for use in a printer, and then the printer print outs the image in accordance with the print data which corresponds to the image data.
When an image is displayed on the monitor device of the PC, the image consists of a plurality of pixels. Each of the pixels has gradation data representing brightness of three primary colors (i.e., R: red; G: green; and B: blue). However, there are various kinds of monitor devices having different characteristics. Therefore, the same RGB data may be displayed differently depending on the monitor devices.
In order to have the image displayed to have the same color in any monitor device, L*a*b* data has recently been employed. The L*a*b* format data includes gradation data of L* value (brightness value), a* value (degree of a change of colors from red to green) and b* value (degree of a change of colors from blue to yellow) for each pixel. For each monitor device, a conversion table from the RGB values to the L*a*b* values (which is referred to as a color profile), and a color of a pixel defined by L*a*b* data appears to have the same color regardless of the monitor devices.
In an output device of the image data (e.g., a printer), conventionally, colors have been expressed using CMY format data or CMYK format data. In the CMY format, a color of a pixel is divided in to three primary colors (C: cyan; M: magenta; and Y: yellow), and is represented by gradation data of each color component. In the CMYK format, in addition to the three primary colors, a component of K (black) is introduced (i.e., a color is represented by gradation data of four color components).
When image data is output (i.e., printed out) using an output device (e.g., a printer), it is necessary to adjust the colors displayed on the monitor device and printed by the output device. For this purpose, conventionally, a conversion table (a color profile) has been employed. For example, a method of converting RGB format data to the CMY format is disclosed in Japanese Patent Provisional Publication No. SHO59-41227, or a method disclosed in Japanese Patent Provisional Publication No. HEI 06-98161.
When an image is printed on an object such as a fabric (e.g., a T-shirt), it will be washed after the image has been printed. In such a case, color-dulling may occur. Additionally, depending on a type of the fabric, a condition of a surface changes (e.g., shagging occurs/suppressed), which results in the appearance of the fabric in terms of the color of the printed image. Thus, the resultant image becomes different from a result expected before in terms of its color.
Another problem is that, when a printing operation is repeated to print the same image, there occurs variations in the printed images. Further, in some cases, an expected print result cannot be achieved. It is because, when the printing operation is performed, there are factors which affect on the print result by varying a printing environment. For example, the factors that affect the print result may include a temperature, humidity, a type (kind) of the object and a printing resolution. Depending on the settings of such factors, the printing environment differs (e.g., penetrating and/or drying characteristics are changed), which may results in the print results.
Conventionally, a method has been suggested to deal with the change of the printing environment by compensating for the print data. For example, when the print data is created based on image data, a compensation is incorporated taking the environment when the printing is executed, thereby appropriate print data corresponding to the environment being created. Using the print data thus create, a desired printing result can be obtained.
Further, according to a conventional technique, the temperature and humidity inside the printer are measured, and if the measured values have been varied, density compensation data corresponding to the changed environment condition is selected. Then, referring to a thickness density compensation table, which has been prepared by measuring a plurality of levels of thickness density values and created based thereon, the thickness density when printing is compensated, the change of the environment condition is dealt with. An example of such a compensation method is disclosed in Japanese Patent Provisional Publication P2001-341394A.
According to Japanese Patent Provisional Publication P2003-1876A, the temperature and humidity inside the printer are measured, and print control information such as ink duty, color conversion table, path rest duration is selected, with which the printing operation is controlled. Then, variation of image quality due to the variation of the temperature and/humidity inside the printer and type of a recording sheet can be compensated.
The above examples in which the print data is preliminary compensated are effective if a time period from an instruction to print at the PC to the start of the printing at the printer is relatively short. However, if the time period is relatively long, the environment may change after the compensated print data is created and before the printing operation is executed.
In particular, the above problem is significant when the compensated data is used in business inkjet printers for fabrics. Such printers are typically configured such that the print data created by a PC is stored in the inkjet printer, and the printing operations are executed by a plurality of times but intermittently in accordance with the same print data as stored. Since the print data is created independent of the printing environment, and the printing operations are executed intermittently, the environment when each printing operation is executed may be different from the environment the print data corresponds to. Therefore, in this case, the print data may not be effected even if the data is compensated for.
Further, publications P2001-341394A and P2003-1876A are intended such that print data is compensated for immediately before the printing operation is executed. Therefore, a processing time period prior to the printing operation is elongated in comparison with a case where such compensation is not executed. For a use, it means that a time period necessary for a data processing prior to the printing is elongated, which requires the user to wait for a longer period after the user has instructed to start the printing operation. Additionally, during such a waiting time, the printing environment may further change and the effectiveness of the compensation may decrease.
If the above compensation method is applied to the business inkjet printer for fabrics as described above, the compensation process is executed at every execution of the printing operation. Therefore, not only at each printing operation but the entire processing time period is elongated.